# Fileserver

The fileserver is a simple frontend to a disk storage space that contains 
auxiliary files for assignments, files submitted by users and evaluation 
results. For a description of the communication protocol used by the frontend 
and workers, see the [Communication](#communication) chapter

## Description

The storage is implemented in Python, using the Flask web framework. This 
particular implementation evolved from a simple mock fileserver we used in early
stages of development.

### Internal storage structure

Fileserver stores its data in a configurable filesystem folder. This folder has 
the following subfolders:

- `./submissions/<id>` - folders that contain files submitted by users 
  (student's solutions to assignments). `<id>` is an identifier received from 
  the ReCodEx API.
- `./submission_archives/<id>.zip` - ZIP archives of all submissions. These are 
  created automatically when a submission is uploaded. `<id>` is an identifier 
  of the corresponding submission.
- `./tasks/<subkey>/<key>` - supplementary task files (e.g. test inputs and 
  outputs). `<key>` is a hash of the file content (sha-1 is used) and `<subkey>` 
  is its first letter (this is an attempt to prevent creating a flat directory 
  structure).

## Installation

To install and use the fileserver, it's necessary to have Python and Pip 
installed.

1. Clone this repository
2. Install dependencies using `pip`

```
pip install -r requirements.txt
```

## Configuration and usage

There are several ways of running the ReCodEx fileserver. We'll cover two 
typical use cases.

### Running in development mode

For simple development usage, it's possible to run the fileserver in the command 
line:

~~~~~~~~~~~~~~~
python3 fileserver.py runserver
~~~~~~~~~~~~~~~

When run like this, the fileserver creates a temporary directory where it stores 
all the files and which is deleted when it exits. It's possible to configure it 
to use any other directory. Use the `--help` flag for a complete list of options 
(such as the port where the server listens).

### Running with uWSGI and a web server

If you need features such as HTTP authentication or efficient serving of static 
files, it is recommended to run the app in a full-fledged web server (such as 
Apache or Nginx) using WSGI. Following examples are simplified, use the `--help` 
flag of the `mkconfig.py` script to see all available options.

### Running using uWSGI

1. (Optional) Create a user for running the fileserver
2. Make sure that your user can access your clone of the repository
3. Run `python mkconfig/mkconfig.py uwsgi --port PORT --user YOUR_USER 
   --working-directory DIR`
4. Save the configuration file generated by the script and run it with uWSGI, 
   either directly or using systemd. This depends heavily on your distribution
5. To integrate this with another web server, see the [uWSGI 
   documentation](http://uwsgi-docs.readthedocs.io/en/latest/WebServers.html)

Note that the ways distributions package uWSGI can vary wildly. In Debian 8 it's 
necessary to convert the configuration file to XML and make sure that the 
python3 plugin is loaded instead of python. This plugin also uses Python 3.4, 
even though the rest of the system uses Python 3.5 - make sure to install 
dependencies for the correct version.